Dubai, part of the UAE, is home to Jebel Ali, a huge man-made port with the largest free-trade zone in the region and 5,500 resident companies. A new airport will be the world's largest. Dubai's state-of-the-art air cargo village helps ensure the world’s fastest sea-air transport in as little as 4 hours. There are no foreign exchange controls, quotas or trade barriers. Import duties are extremely low, and many products are exempt. The UAE dirham is freely convertible and is linked to the US dollar. Other tax-free zones in Dubai include the Dubai International Financial Centre (DIFC), a financial centre with nearly 1,000 international financial institutions, and Dubai Internet City, which already hosts 1,400 resident companies. Apart from the oil industry and domestic banking, there are no income or capital taxes in Dubai, and no withholding tax. Dubai has a number of double tax treaties with high-tax countries and is often used in international tax planning by major corporations.